HPIPM:Rhizoctonia solani (Dry beans)

Author: Howard F. Schwartz, David H. Gent, Gary D. Franc and Robert M. Harveson

Taxonomy

Domain	Eukarya
Kingdom	Fungi
Phylum	Basidiomycota
Subphylum	Agaricomycotina
Class	Agaricomycetes
Order	Cantharellales
Family	Ceratobasidiaceae
Genus	Rhizoctonia

Scientific Name

Rhizoctonia solani

Scientific Name Synonyms

Moniliopsis aderholdii

Corticium solani

Rhizoctonia napaeae

Thanatephorus cucumeris

Common Name

Rhizoctonia damping-off, blight and rot

Identification and Life Cycle

Rhizoctonia root rot is caused by the fungus Rhizoctonia solani. The fungus survives in infected plant debris, and inoculum concentrations in the soil are increased by continually cropping fields to susceptible crops such as dry bean, potato and sugarbeet. Rhizoctonia is spread within and between fields by irrigation water and soil movement. Rhizoctonia root rot of germinating seedlings is favored by moderate to high soil moisture and low soil temperatures. Damage is generally restricted to young seedlings, but can affect older plants, especially when the plants are stressed by extremes in temperature between warm soil and cool water from deep irrigation wells.

Plant Response and Damage

Rhizoctonia solani can cause seedling death, root and hypocotyl rot, stem cankers and pod rot. Initial symptoms appear on roots or hypocotyls as linear or circular reddish-brown sunken lesions or cankers delimited by a brown to reddish-brown margin. Rhizoctonia cankers enlarge with age, become darker, rough textured, and retard plant growth. The fungus can invade the central part of the lower stem and produce a brick-red discoloration. Disease symptoms often occur on scattered plants in a somewhat circular field pattern. Severe seedling infection causes plant death. Rhizoctonia cankers enlarge with age, become darker, rough textured, and retard plant growth. Later in the season, mixed infection with Fusarium and Pythium root rot organisms are common. Lesions may also develop on pods that are in contact with the moist soil surface and cause pod rotting or seed discoloration.

Biological Control

Deny (Burkholderia cepacia) is registered for protection of dry bean roots from Fusarium, Rhizoctonia, and Pythium spp. T-22 Planter Box (Trichoderma harzianum strain KRL-AG2) is registered, but cannot by used in alkaline or cold soils. The efficacy of these biological control agents in the High Plains is not known. Cultural Control

Plant high quality seed in warm (greater than 60°F), well-prepared seedbeds under conditions favorable to rapid seedling emergence; shallow planting can encourage rapid emergence. Avoid excess irrigation and poor drainage. Crop rotation with non-hosts (i.e., small grains) may provide some reduction in Rhizoctonia root rot. Conventional tillage that incorporate previous crop residue deeply and early can to promote complete decomposition before planting and reduce Rhizoctonia root rot.

Chemical Control

Chemical controls are most effective when combined with sound cultural practices.

Due to constantly changing labels, laws and regulations, the sponsors of this web site assume no liability for the suggested use of any chemicals noted in the management section. Contact your local pest management personnel for current information on labeled pesticides that can be used for the intended plant disease, insect pest or weed.